1. Field of the Invention
The present invention relates to coupling joint structure of a small-sized boat where respective couplers are provided to an output shaft and a propeller shaft, a damper member is interposed between each coupler and the revolution of the output shaft is transmitted to the propeller shaft via the damper member.
2. Description of Background Art
A small-sized boat is provided in which an engine is mounted in the body of the boat, a water jet pump is provided at the back of the engine and an output shaft of the engine is coupled to a propeller shaft of the water jet pump via a coupling.
The revolution of the output shaft is transmitted to the propeller shaft via the coupling by revolving the engine, water is sucked from the bottom of the boat by driving the water jet pump, the sucked water is jetted backward, and the boat is glided (for example, refer to JP-A No. 255492/2000).
Referring to FIG. 7, JP-A No. 255492/2000 will be described below.
FIG. 7 is an explanatory drawing for explaining conventional type basic configuration.
A coupling joint 100 is provided with a coupler 103 on the driving side to an output shaft 102 of an engine 101 and a coupler 105 on the driven side to a propeller shaft 104 of a propeller, pawl pieces 107 - - - ( - - - denotes plural pieces) on the driving side are extended from the body 106 of the coupler 103 on the driving side toward the rear of the boat, pawl pieces 109 - - - on the driven side are extended from the body 108 of the coupler 105 on the driven side toward the front of the boat, and a damper member 111 is interposed between the pawl pieces 107 - - - on the driving side and the pawl pieces 109 - - - on the driven side.
The revolution of the output shaft 102 is transmitted to the damper member 111 via the coupler 103 on the driving side by revolving the engine 101 and the revolution of the engine 101 is transmitted to the propeller shaft 104 by transmitting the revolution of the damper member 111 to the coupler 105 on the driven side.
The revolution of the output shaft 102 is transmitted to the damper member 111 via the pawl pieces 107 - - - on the driving side of the coupler 103 on the driving side and is transmitted to the pawl pieces 109 - - - on the driven side of the coupler 105 on the driven side via the damper member 111.
To securely transmit large torque from the output shaft 102 to the propeller shaft 104, each sectional shape of the pawl pieces 107 - - - on the driving side and the pawl pieces 109 - - - on the driven side is enlarged and the strength is required to be secured.
However, when each sectional shape of the pawl pieces 107 - - - on the driving side and the pawl pieces 109 - - - on the driven side is enlarged, the weight of each pawl piece 107 - - - , 109 - - - increases.
When the weight of each pawl piece 107 - - - , 109 - - - increases, the centrifugal force of the pawl pieces 107 - - - on the driving side and the pawl pieces 109 - - - on the driven side increases when the coupling joint 100 is revolved.
Therefore, it is difficult to secure the durability of the pawl pieces 107 - - - , 109 - - - with centrifugal force.